Static induction type thyristor

Abstract

In a static induction type thyristor comprising a low impurity concentration channel region having opposed first and second major surfaces, a first main electrode region having one conductivity type and a second main electrode region having another conductivity type opposite to the one conductivity type and provided on the first and second major surfaces, respectively, and a gate region provided in the vicinity of the first main electrode region, there intervenes, between the channel region and the second main electrode region, a thin layer region having the same conductivity type as that of first main electrode region. The provision of this thin layer region contributes to allowing a markedly low impurity concentration as well as a decreased thickness of the channel region for a given maximum forward blocking voltage, making it feasible to obtain a high maximum forward blocking voltage and a high switching speed.

What is claimed is: 
     
       1. A static induction type thyristor comprising: a high-resistivity semiconductor substrate region;   a cathode region provided on one of major surfaces of said substrate region;   a anode region provided on the other of said major surfaces of said substrate region and being formed by a high impurity concentration region of a conductivity type contrary to that of said cathode region;   a junction gate region provided in the vicinity of said cathode region on said one major surface of said substrate region and being formed by a high impurity concentration region of a same conductivity type as that of said anode region; and   a thin layer region provided between said anode region and substrate region and having a conductivity type contrary to that of said anode region and having its thickness l 2  and its impurity concentration N D1 ,   a p-n junction being formed between said anode region and said thin layer substantially over the entire of said substrate region, and   the thickness l 3  and impurity concentration N D2  of said thin layer region being so selected as to satisfy the following formulae (1) and (2) and that the maximum forward blocking voltage V Bamax  may be given approximately by the following formula (3): ##EQU7##  wherein the reference symbol E qs  represents the intensity of the electric field at said substrate region in the vicinity of said junction gate region, the reference symbol E s  represents the breakdown electric field at which avalanche begins to take place, the reference symbol l 2  represents the thickness of said substrate region between said junction gate region and said thin layer region, the reference symbol N D1  represents the impurity concentration of said substrate region between said junction gate region and said thin layer region, the reference symbol ε represents the dielectric constant of said substrate gion, and the reference symbol q represents the magnetude of the electronic charge.   
     
     
       2. A static induction type thyristor according to claim 1, in which: said junction gate region is a flat surface gate type region being formed by diffusion from a same major surface as the major surface on which said cathode region is provided.   
     
     
       3. A static induction type thyristor according to claim 1, in which: said junction gate region is a buried gate type region buried into said substrate region in the vicinity of said cathode region.   
     
     
       4. A static induction type thyristor according to claim 1, in which: said junction gate region is a split gate type region formed on the bottom surface of a groove split from the major surface on which said cathode region is provided.   
     
     
       5. A static induction type thyristor according to claim 1, in which: said junction gate region is a split gate type region formed on the side surface of a groove split from the major surface on which said cathode region is provided.   
     
     
       6. A static induction type thyristor according to claim 1, in which: said substrate region is formed by a substantially intrinsic semiconductor region, the maximum forward blocking voltage and a reverse breakdown voltage are respectively set at a value near to E s  l 2  /2 by selecting the thickness l 3  and the impurity concentration N D2  so that the following formula (4) is satisfied: ##EQU8##   
     
     
       7. A static induction type thyristor according to claim 1 or 2, further in which: an insulating layer interposed between said junction gate region and said cathode region opposed to each other.   
     
     
       8. A static induction type thyristor according to claim 7, in which: an insulating layer provided just below the bottom portion of said junction gate region near to said cathode region.   
     
     
       9. A static induction type thyristor according to claim 7, in which: an insulating layer provided just below the bottom portion of said junction gate region near to said cathode region.   
     
     
       10. A static induction type thyristor according to claim 7, in which: a semiconductor region provided just below the bottom portion of said junction gate region near to said cathode region and having a conductivity contrary to that of said junction gate region and an impurity concentration less than that of said junction gate region.   
     
     
       11. A static induction type thyristor according to claim 7, in which a predetermined amount of a substance having a killer effect is added to one of said substrate region and said thin layer region.   
     
     
       12. A static induction type thyristor according to claim 7, in which: a main electrode is connected in series to a Schottky diode or a p +  in +   diode each having a predetermined reverse breakdown voltage to enable to have a further reverse breakdown voltage.   
     
     
       13. A static induction type thyristor according to claim 7, in which: ##EQU9## and the maximum reverse breakdown voltage Varmax is given by the following formula (6). ##EQU10## 
     
     
       14. A static induction type thyristor according to claim 1 or 2, in which: an insulating layer provided just below the bottom portion of said junction gate region near to said cathode region.   
     
     
       15. A static induction type thyristor according to claim 14, in which: an insulating layer provided just below the bottom portion of said junction gate region near to said cathode region.   
     
     
       16. A static induction type thyristor according to claim 14, in which: a predetermined amount of a substance having a killer effect is added to one of said substrate region and said thin layer region.   
     
     
       17. A static induction type thyristor according to claim 14, in which: said substrate region is formed by a substantially intrinsic semiconductor region, the maximum forward blocking voltage and a reverse breakdown voltage are respectively set at a value near to E s  l 2  /2 by selecting the thickness l 3  and the impurity concentration N D2  so that the following formula (4) is satisfied: ##EQU11##   
     
     
       18. A static induction type thyristor according to claim 14, in which: a main electrode is connected in series to a Schottky diode or a p +  in +   diode having a predetermined reverse breakdown voltage to enable to have a further reverse breakdown voltage.   
     
     
       19. A static induction type thyristor according to claim 14, in which: ##EQU12## and the maximum reverse breakdown voltage Varmax is given by the following formula (6). ##EQU13## 
     
     
       20. A static induction type thyristor according to claim 1 or 2, in which: said junction gate region has a wider region at a position being away from said major surface of said substrate region.   
     
     
       21. A static induction type thristor according to claim 20, in which: said substrate region is formed by a substantially intrinsic semiconductor region, the maximum forward blocking voltage and a reverse breakdown voltage are respectively set at a value near to E s  l 2  /2 by selecting the thickness l 3  and the impurity concentration N D2  so that the following formula (4) is satisfied: ##EQU14##   
     
     
       22. A static induction type thyristor according to claim 20, in which: a main electrode is connected in series to a Schottky diode or a p +  in +   diode each having a predetermined reverse breakdown voltage to enable to have a further reverse breakdown voltage.   
     
     
       23. A static induction type thyristor according to claim 20, in which: ##EQU15## and the maximum reverse breakdown voltage Varmax is given by the following formula (6). ##EQU16## 
     
     
       24. A static induction type thyristor according to claim 1 or 2, in which: a semiconductor region provided just below the bottom portion of said junction gate region near to said cathode region and having a conductivity contrary to that of said junction gate region and an impurity concentration less than that of said junction gate region.   
     
     
       25. A static induction type thyristor according to claim 24, in which: a predetermined amount of a substance having a killer effect is added to one of said substrate region and said thin layer region.   
     
     
       26. A static induction type thristor according to claim 24, in which: said substrate region is formed by a substantially intrinsic semiconductor region, the maximum forward blocking voltage and a reverse breakdown voltage are respectively set at a value near to E s  l 2  /2 by selecting the thickness l 3  and the impurity concentration N D2  so that the following formula (4) is satisfied: ##EQU17##   
     
     
       27. A static induction type thyristor according to claim 24, in which: a main electrode is connected in series to a Schottky diode or a p +  in +   diode each having a predetermined reverse breakdown voltage to enable to have a further reverse breakdown voltage.   
     
     
       28. A static induction type thyristor according to claim 24, in which: ##EQU18## and the maximum reverse breakdown voltage Varmax is given by the following formula (6). ##EQU19## 
     
     
       29. A static induction type thyristor according to claim 1 or 2, in which: a semiconductor region provided on a part of said junction gate region is contact with said substrate region and having a conductivity contrary to that of said junction gate region and an impurity concentration less than that of said junction gate region, and   said semiconductor region being formed so as to be relatively thick at the bottom portion of said junction gate region and to be thin at the side portion of said junction gate region.   
     
     
       30. A static induction type thyristor according to claim 29, in which: a predetermined amount of a substance having a killer effect is added to one of said substrate region and said thin layer region.   
     
     
       31. A static induction type thyristor according to claim 29, in which: said substrate region is formed by a substantially intrinsic semiconductor region, the maximum forward blocking voltage and a reverse breakdown voltage are respectively set at a value near to E s   l   2  /2 by selecting the thickness l 3  and the impurity concentration N D2  so that the following formula (4) is satisfied: ##EQU20##   
     
     
       32. A static induction type thyristor according to claim 29, in which: a main electrode is connected in series to a Schottky diode or a p +  in +   diode each having a predetermined reverse breakdown voltage to enable to have a further reverse breakdown voltage.   
     
     
       33. A static induction type thyristor according to claim 29, in which: ##EQU21## and the maximum reverse breakdown voltage Varmax is given by the following formula (6). ##EQU22## 
     
     
       34. A static induction type thyristor according to claim 1, 2, 3, 4 or 5, in which: a predetermined amount of a substance having a killer effect is added to one of said substrate region and said thin layer region.   
     
     
       35. A static induction type thyristor according to claim 34, in which: a main electrode is connected in series to a Schottky diode or a p +  in +   diode each having a predetermined reverse breakdown voltage to enable to have a further reverse breakdown voltage.   
     
     
       36. A static induction type thyristor according to claim 34, in which: ##EQU23## and the maximum reverse breakdown voltage Varmax is given by the following formula (6). ##EQU24## 
     
     
       37. A static induction type thyristor according to claim 1, 2, 3, 4 or 5, in which: a main electrode is connected in series to a Schottky diode or a p +  in +   diode each having a predetermined reverse breakdown voltage to enable to have a further reverse breakdown voltage.   
     
     
       38. A static induction type thyristor according to claim 1, 2, 3, 4 or 5, in which: the maximum reverse breakdown voltage Varmax is applied between said anode region and said cathode region,   each value of N D1 , l 2 , N D2  and l 3  is selected so as to satisfy the following formula (5) to enable a depletion layer expanded within said substrate region to attain into the vicinity of said junction gate region from said anode region, when the maximum electric field intensity E max  of a p-n junction surface formed between said anode region and said thin layer has become approximately equal to the intensity of the breakdown electric field E s , ##EQU25## and the maximum reverse breakdown voltage Varmax is given by the following formula (6). ##EQU26##